netdev - [PATCH bpf] bpftool: Don't crash on missing jited insns or ksyms

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Message-Id: <20191210143047.142347-1-toke@redhat.com>
Date:   Tue, 10 Dec 2019 15:30:47 +0100
From:   Toke Høiland-Jørgensen <toke@...hat.com>
To:     Daniel Borkmann <daniel@...earbox.net>,
        Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc:     Toke Høiland-Jørgensen <toke@...hat.com>,
        netdev@...r.kernel.org, bpf@...r.kernel.org
Subject: [PATCH bpf] bpftool: Don't crash on missing jited insns or ksyms

When JIT hardening is turned on, the kernel can fail to return jited_ksyms
or jited_prog_insns, but still have positive values in nr_jited_ksyms and
jited_prog_len. This causes bpftool to crash when trying to dump the
program because it only checks the len fields not the actual pointers to
the instructions and ksyms.

Fix this by adding the missing checks.

Signed-off-by: Toke Høiland-Jørgensen <toke@...hat.com>
---
 tools/bpf/bpftool/prog.c          | 2 +-
 tools/bpf/bpftool/xlated_dumper.c | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/tools/bpf/bpftool/prog.c b/tools/bpf/bpftool/prog.c
index 4535c863d2cd..2ce9c5ba1934 100644
--- a/tools/bpf/bpftool/prog.c
+++ b/tools/bpf/bpftool/prog.c
@@ -493,7 +493,7 @@ static int do_dump(int argc, char **argv)
 
 	info = &info_linear->info;
 	if (mode == DUMP_JITED) {
-		if (info->jited_prog_len == 0) {
+		if (info->jited_prog_len == 0 || !info->jited_prog_insns) {
 			p_info("no instructions returned");
 			goto err_free;
 		}
diff --git a/tools/bpf/bpftool/xlated_dumper.c b/tools/bpf/bpftool/xlated_dumper.c
index 494d7ae3614d..5b91ee65a080 100644
--- a/tools/bpf/bpftool/xlated_dumper.c
+++ b/tools/bpf/bpftool/xlated_dumper.c
@@ -174,7 +174,7 @@ static const char *print_call(void *private_data,
 	struct kernel_sym *sym;
 
 	if (insn->src_reg == BPF_PSEUDO_CALL &&
-	    (__u32) insn->imm < dd->nr_jited_ksyms)
+	    (__u32) insn->imm < dd->nr_jited_ksyms && dd->jited_ksyms)
 		address = dd->jited_ksyms[insn->imm];
 
 	sym = kernel_syms_search(dd, address);
-- 
2.24.0